Microtubule dynamic instability controls podosome patterning in osteoclasts through EB1, cortactin, and Src

Area of Science:

• Cell Biology
• Bone Biology
• Cytoskeletal Dynamics

Background:

• Osteoclasts (OCs) utilize podosomes organized in a belt, a structure essential for bone resorption.
• Microtubules (MTs) are known to influence podosome belt formation and stability, but the mediating molecules remain unidentified.
• Plus-end tracking proteins (+TIPs) are candidates for regulating podosome patterning due to MT plus-end orientation.

Purpose of the Study:

• To identify the molecules mediating the interaction between microtubules and podosomes in osteoclasts.
• To investigate the role of EB1 and cortactin in the organization of the podosome belt and bone resorption.

Main Methods:

• Observed EB1 localization and MT targeting to podosomes in mature osteoclasts.
• Manipulated MT dynamic instability, EB1 function, and cortactin levels/activity.
• Assessed podosome belt integrity, MT-podosome interactions, and bone resorption activity.

Main Results:

• EB1 is enriched in the podosome belt, and EB1-positive MTs target podosomes; EB1 depletion or disruption of MT dynamics destabilizes the podosome belt.
• Cortactin interacts with EB1 in an Src-dependent manner.
• Cortactin deficiency impairs MT targeting to podosomes, podosome patterning, and bone resorption; altered MT dynamics affect cortactin phosphorylation and acetylation.

Conclusions:

• Dynamic microtubules, regulated by EB1, are critical for establishing and maintaining the osteoclast podosome belt.
• Cortactin acts as a key mediator, linking microtubule dynamics to podosome organization and function.
• The interplay between dynamic MTs and podosomes, involving EB1 and cortactin, is essential for effective bone resorption.